1. Field
One embodiment of the present invention relates to a method of manufacturing a magnetic recording medium such as a patterned medium.
2. Description of the Related Art
Recently, in magnetic recording media installed in hard disk drives (HDDs), there is an increasing problem of disturbance of enhancement of track density due to interference between adjacent tracks. In particular, a serious technical subject is reduction of a fringe effect of a field from a write head.
To solve such a problem, a discrete track recording-type patterned medium (DTR medium), for example, has been proposed in which recording tracks are physically separated by processing a ferromagnetic layer. The DTR medium can reduce a side erase phenomenon, i.e., erasing information of an adjacent track in writing, and a side read phenomenon, i.e., reading out information of an adjacent track in reading, making it possible to enhance the track density. Therefore, the DTR medium is expected as a magnetic recording medium capable of providing a high recording density. Similarly, a bit patterned medium (BPM) having dot-like magnetic patterns is also expected as a magnetic recording medium capable of providing high recording density.
A known method of manufacturing a patterned medium (DTR medium or BPM) comprises forming a hard mask made of carbon and a resist on the magnetic recording layer, imprinting a stamper to the resist to transfer patterns of protrusions and recesses, etching the hard mask using the resist pattern as a mask to transfer patterns of protrusions and recesses, and etching the magnetic recording layer using the hard mask pattern as a mask to form patterns of protrusions and recesses.
Jpn. Pat. Appln. KOKAI Publication Nos. 2005-50468 and 2005-56535 disclose a step of removing a hard mask entirely by using an ashing apparatus and a reactive etching apparatus. However, if the hard mask is removed entirely by ashing or reactive ion etching, plasma distribution tends to be unstable in the vicinity of the edges of the magnetic recording layer forming protrusions and recesses. Thus, nonuniformity of the plasma distribution causes formation of a damage layer on the surface of the magnetic recording layer when the hard mask is removed. If the damage layer is formed on the surface of the magnetic recording layer in this manner, there is a problem that effective magnetic spacing is so increased that only insufficient read characteristics can be obtained when the medium is installed in a hard disk drive.